LMV
Series
Technical
Instructions
Document
No.
LV5
‐
1000
SCC
Inc.
Page
17
Section
5
The
LMV52
/
VFD
/
blower
response
can
be
watched
to
check
for
proper
operation.
This
can
be
done
in
standby
Phase
12
(burner
off)
by
using
the
following
menu
path:
Params
&
Display
>
RatioControl
>
Gas/Oil
Settings
>
CurveParams
or
Curve
Settings
When
the
blower
is
at
a
speed
other
than
what
is
displayed,
an
arrow
(>)
is
displayed
on
the
AZL
next
to
the
VFD
position.
When
the
blower
is
at
the
displayed
speed,
a
colon
(:)
is
displayed
on
the
AZL
next
to
the
VFD
position.
By
ramping
the
VFD
up
and
down,
the
response
of
the
VFD
can
be
observed.
Transitioning
back
and
forth
between
a
colon
(:)
and
a
(>)
after
ramping
the
VFD
up
or
down
indicates
a
speed
control
issue.
The
LMV52's
closed
loop
speed
control
is
based
on
PI
(proportional
‐
integral)
logic.
The
response
of
this
loop
can
be
tuned
using
the
following
menu
path:
Params
&
Display
>
VSD
Module
>
Configuration
>
Speed
>
Setteling
Time
In
most
cases,
this
does
not
need
to
be
tuned.
See
Section
3
(Parameters)
for
a
full
explanation.
The
absolute
speed
as
read
in
real
time
by
the
speed
wheel
can
be
watched
at
any
point
in
time.
When
the
LMV52
is
not
modulating
or
when
it
is
at
a
fixed
VFD
speed
(pre
‐
purge,
post
‐
purge,
ignition,
etc.),
the
speed
should
be
steady,
not
deviating
by
more
than
+/
‐
10
RPM.
This
can
be
viewed
at:
Params
&
Display
>
VSD
Module
>
Configuration
>
Speed
>
Absolute
Speed
The
combustion
air
pressure
switch
should
be
set
by
taking
the
VFD
to
10%
below
the
lowest
anticipated
low
fire
speed
(if
low
fire
is
50%,
take
the
VFD
to
40%)
and
setting
the
switch
to
open
at
that
point.
This
should
maximize
the
safety
potential
of
the
combustion
air
pressure
switch
and
minimize
nuisance
trips.
This
can
be
done
in
standby
by
setting
the
home
position
of
the
VFD
to
40%
and
setting
the
switch.
In
most
applications
with
an
air
damper,
there
is
little
reason
to
decrease
blower
speed
below
about
50%
VFD
(30
Hz).
Power
consumption
decreases
by
the
cube
of
the
RPM
even
without
the
additional
restriction
of
an
air
damper.
Referencing
information
from
the
"Centrifugal
Blower
Fundamentals"
section
on
the
previous
pages,
decreasing
the
speed
of
a
25
HP
(18.62
kW)
motor
from
3600
RPM
(60
Hz)
to
1800
RPM
(30
Hz)
will
cause
the
power
consumption
to
be
reduced
from
18.62
kW
down
to
2.32
kW,
an
electrical
savings
of
over
800%.
A
VFD
alone
without
an
air
damper
or
sliding
head
offers
limited
accuracy
and
repeatability
for
the
airflow
at
higher
burner
turndowns.
For
most
boiler
burners,
modulating
the
VFD
alone
without
an
air
damper
is
okay
for
turndowns
of
4
‐
to
‐
1
or
less.
Using
only
a
VFD
for
airflow
regulation
at
higher
turndowns
may
lead
to
airflow
repeatability
issues.
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Summary of Contents for LMV 5 Series
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